Implantable medical devices, such as cardiac rhythm management (CRM) devices and neuromodulation devices, are used in a variety of therapeutic applications. In some applications, one or more implantable electrical leads are employed to deliver therapy from an implanted medical device to tissues within a body. CRM systems may employ electrical leads implanted within a patient's heart. It is often the case that such leads are secured to a desired location in the heart by a mechanical device. Such mechanical fixation devices may include a corkscrew-shaped device known as a helix. The helix may be designed such that it is retracted into the lead during insertion and positioning within the heart. Once positioned, the helix is rotated to extend the helix and screw it into the heart muscle.
Helix rotation may be driven by torque applied to a terminal pin and transmitted through a conductor coil extending through the lead from the terminal pin to the helix. Terminal pins are often quite small and have smooth, cylindrical surfaces. This presents some difficulty in applying a desired amount of torque to ensure a number of rotations necessary to properly seat the helix. Fixation tools are often used to apply torque to the terminal pin. Improved fixation tools may more reliably apply torque to the terminal pin.